The present invention relates to stable, injectable aqueous solutions of peptides such as glucagon, glucagon-like peptide-1 (GLP-1, e.g. GLP-1(7-37) and GLP-1(7-36) amide) and analogues and derivatives thereof.
Glucagon and glucagon-like peptide 1 (GLP-1) are polypeptide hormones both derived from proglucagon. Upon tissue-specific processing, glucagon is produced in the pancreas, while GLP-1 is predominantly secreted in the intestine. Physiologically, both peptides play major roles in the regulation of blood glucose. Glucagon is directly involved via glycogenolytic as well as gluconeogenetic effects. GLP-1 is indirectly involved via stimulation of insulin and inhibition of glucagon secretion. Thus, the two peptides affect the blood glucose in opposite directions.
Due to its glycogenolytic effect on the liver, glucagon is used for the treatment of acute hypoglycemia (e.g. xe2x80x9cinsulin shockxe2x80x9d). In addition, glucagon excerts a spasmolytic effect on smooth muscles, and this effect is used clinically in connection with several imaging procedures, especially radiology.
GLP-1 fragments such as GLP-1 (7-37), GLP-1 (7-36) amide and functional analogues thereof (hereinafter designated GLP-1 compounds) stimulate pancreatic insulin release in the presence of glucose, and this finding suggests that GLP-1 compounds may be useful in the treatment of type II diabetes.
Glucagon (29 amino acids; see e.g. The Merck Index, 10th Edition for the amino acid sequence) and GLP-1 compounds (typically about 29-31 amino acids) are single chain highly homologous peptides. While little information is available on the solution behaviour of GLP-1 compounds, the physico-chemical properties of glucagon are well described in the literature (J.Biol.Chem. 244, 6675-6679 (1969); Nature 257, 751-757 (1975); FEBS Letts. 119, 265-270 (1980)). The peptide exhibits very low solubility in water at a pH in the range of about 4-9. Outside this region, aqueous solutions are generally metastable and prone to gel formation or flocculation within hours of their preparation.
Accordingly, glucagon compositions for injection are currently marketed in the form of a lyophilized powder which is to be reconstituted using a suitable diluent shortly before use. The resulting acidic solution may then be injected. In contrast with the single-dose compositions of glucagon used for acute hypoglycemia and the motility indication in radiology, the utility of GLP-1 compounds for the treatment of type II diabetes generally involves multiple-dose soluble compositions. Given the instability of glucagon, the formulation of such compositions is inherently difficult.
Thus, there is a need for stable aqueous formulations of peptides such as glucagon and GLP-1 compounds. In the case of glucagon, the availability of a ready-to-use composition is desirable for emergency treatment of acute hypoglycemia, enabling the patient or another person present to treat the hypoglycemic incidence immediately. Also for the mobility indication for glucagon used in radiology, and for the type II diabetes indication for GLP-1 compounds, the availability of a ready-to-use aqueous composition provides obvious advantages in terms of convenience and safety.
Glucagon compositions solubilized by the addition of detergent have received relatively little attention in the literature. British patent No. 1 202 607 describes the use of either cationic (quarternary ammonium bases) or anionic (alkyl-aryl-sulphonates), monovalent detergents. These compounds provide enhanced solubilization of 1 mg/ml glucagon over a limited pH range using a 6-fold molar excess of detergent.
A series of other studies on glucagon-detergent interactions employ much lower glucagon concentrations and do not address the effect of detergent on peptide solubility. Thus, in studies using 0-200 xcexcM of the amphoteric (twitterionic) detergent hen egg lysolecithin, binding of detergent was shown to induce partial helical structure in solutions of glucagon containing about 0.02 mg/ml peptide (J.Biol.Chem. 247, 4986-4991; 4992-4995; (1972)). Similarly, in studies employing dilute (0.005-0.05 mg/ml) solutions of glucagon, lysolecithin was found more efficient than the anionic detergents dipalmitoyl phosphatidic acid and sodium dodecyl sulfate (SDS) in inducing partial helical structure in glucagon (Biopolymers 21, 1217-1228 (1982); Biopolymers 22, 1003-1021 (1983)).
At the other extreme, a few examples are available characterizing the interaction between glucagon and concentrated detergent solutions. These include the binding of dilute glucagon to micelles of the anionic detergent SDS at 25 mM, pH 2 (Biochemistry 19, 2117-2122, (1980)), and the solubilization of glucagon (up to 20 mg/ml) via binding to micelles of the amphoteric dodecylphosphocholine present in a 40-fold molar excess (e.g. 3.5 mg/ml glucagon is solubilized using 40 mM detergent at neutral pH; Biochim.Biophys.Acta 603, 298-312, (1980))
With the exception of a single example describing the solubilization of 20 mg/ml GLP-1 (7-36) amide bound to micelles of dodecylphosphocholine at 280 mM (cf. the glucagon case above, Biochemistry 33, 3532-3539, 1994), no reports are available on the binding of detergents by GLP-1 compounds and the resulting effect on peptide solubility and stability. In contrast, several ways of preparing prolonged delivery of GLP-1 compounds have been described (e.g. European patent application No. 0619322 and column 6 of U.S. Pat. No. 5,120,712). The possibilities include use of polymers, incorporation into particles of polymer material or into an oil suspension, addition of zinc ion, protamine sulphate and/or phenolic compounds, and preparation of amorphous/crystalline formulations.
It has now surprisingly been found that soluble and stable formulations of glucagon and GLP-1 compounds may be prepared by means of addition of detergents carrying multiple charges (i.e. two or more negative, two or more positive, or both positive and negative charges). When added in an amount corresponding to e.g. about 0.5-20 moles of detergent per mole of peptide, this class of detergents is capable of solubilizing pharmaceutically relevant concentrations of glucagon and GLP-1 compounds in the entire pH range from 4 to 9. The expanded pH range allows optimal selection of conditions to suppress chemical degradation of the solubilized peptide. Furthermore, preferred detergents consist of naturally occurring building blocks which are more biologically acceptable than those previously described.
Thus, in its broadest aspect, the present invention relates to a pharmaceutical composition in the form of a solution comprising a polypeptide containing an amphiphatic xcex1-helix which is stabilized by interaction with a detergent carrying multiple charges. Such polypeptides include, but are not limited to, glucagon, GLP-1 compounds, corticotropin (ACTH), calcitonin, and functional analogues thereof.
One aspect of the invention relates to an aqueous composition in the form of a solution comprising at least one peptide selected from glucagon, GLP-1, and analogues and derivatives thereof together with a stabilizing and solubilizing amount of at least one detergent, said detergent having at least 2 positive charges, at least 2 negative charges, or a combination of at least one positive charge and at least one negative charge, the peptide or analogue or derivative thereof being present in a concentration of at least about 0.1 mg/ml, with the proviso that the detergent is not dodecyl phosphocholine.
Another aspect of the invention relates to a method for stabilizing an aqueous composition in the form of a solution comprising at least one peptide selected from glucagon, GLP-1 and analogues and derivatives thereof by adding to the composition a stabilizing and solubilizing amount of at least one such detergent having multiple charges.
In a further embodiment, the invention relates to a method for treating insulin dependent or non-insulin dependent diabetes mellitus or obesity in a patient in need of such treatment, comprising administering to the patient a therapeutically effective amount of an appropriate stabilized aqueous composition as described herein.
Glucagon and GLP-1 compounds belong to a class of polypeptides which have the potential of forming amphiphatic helices, i.e., one face of the helical structure displays mainly hydrophobic amino acid side chains, while the other face exposes hydrophilic and/or charged side chains. In polypeptides of this type, the formation of the amphiphatic helical structure is often linked to inter-peptide helix self-association along the interfaces defined by the hydrophobic patches.
A simple system is used to describe fragments and analogues of GLP-1. Thus, for example, Gly8-GLP-1 (7-37) designates a fragment of GLP-1 formally derived from GLP-1 by deleting the amino acid residues Nos. 1 to 6 and substituting the naturally occurring amino acid residue in position 8 (Ala) by Gly. Similarly, Lys34(Nxcex5-tetradecanoyl)-GLP-1 (7-37) designates GLP-1 (7-37) wherein the and-amino group of the Lys residue in position 34 has been tetradecanoylated.
The amino acid sequence of GLP-1 (7-36)amide and GLP-1 (7-37) is as given in the general formula (I) below:
which shows GLP-1 (7-36)amide when X is NH2 and GLP-1 (7-37) when X is Gly-OH.
In the present text, the designation xe2x80x9canaloguexe2x80x9d is used to designate a peptide wherein one or more amino acid residues of the basic GLP-1 peptide have been substituted by another amino acid residue and/or wherein one or more amino acid residues of the peptide have been deleted and/or wherein one or more amino acid residues have been added to the peptide. Such addition can take place either at the N-terminal end or at the C-terminal end or both. The term xe2x80x9cderivativexe2x80x9d is used in the present text to designate a peptide in which one or more of the amino acid residues of the peptide have been chemically modified, e.g. by alkylation, acylation, ester formation or amide formation. For the sake of simplicity, the term xe2x80x9cpeptidexe2x80x9d will generally be used herein to refer to the glucagon and GLP-1 peptides as such as well as analogues and derivatives thereof.
The present invention is based on situations where the hydrophilic patch of the putative amphiphatic helix displays two or more charges. By the addition of a detergent carrying a complementary set of multiple charges, a stabilizing and solubilizing helix-forming effect will result from a combination of two factors, i.e. 1) chargexe2x80x94charge interactions between the polar head of the detergent and the charged amino acid side chains of the helix; and 2) the hydrophobic tail of the detergent serving as a template for association with the hydrophobic patch of the same or that of a neighboring helix.
The stabilized solutions of the invention can be used for parenteral, pulmonal or nasal administration. Such solutions remain stable and retain biological activity when stored at temperatures of e.g. 4xc2x0-25xc2x0 C. for extended periods of time.
Suitable detergents according to the invention are characterized by having multiple charges, i.e. two or more positive charges, two or more negative charges, or a combination of at least one positive charge and at least one negative charge. The advantage of multiple charges as opposed to monovalent ionic detergents is illustrated in the appended FIG. 1. This figure compares the pH-dependence of the equilibrium solubility in 1 mg/ml solutions of glucagon in the absence of additives and in the presence of 1 mM of each of the following detergents: a) cetyl-trimethylammonium bromide (CTAB, i.e. monovalent cationic), b) sodium dodecyl sulfate (SDS, i.e. monovalent anionic) and c) myristoyl lysophosphatidylcholine (LPCM, i.e. amphoteric).
These data show that, while the monovalent cationic and anionic detergents promote solubility at the acidic and basic limbs of the solubility curve, respectively, the amphoteric detergent effects full solubility over the entire pH range. Furthermore, the effect of the amphoteric detergent is clearly much stronger than that expected from the sum of the effects seem with each of the monovalent detergents.
The detergents used in accordance with the present invention contain a polar head group with two or more charges and one or more aliphatic side chains each having at least 6 carbon atoms. In the preferred detergents, any aliphatic side chains have 8-20, e.g. 10-18 carbon atoms. With respect to the polar head group, useful detergents include those selected from the group consisting of lysophospholipids (e.g. 1-acyl-sn-glycero-3-phosphate esters of ethanolamine, choline, serine or threonine). Lauroyl and myristoyl derivatives of lysophosphatidylcholine, lysophosphatidylserine and lysophosphatidylthreonine are particularly useful. Alternatively, the polar group may be a basic amino acid (e.g. Nxcex1-acylated derivatives of lysine, arginine or histidine, or side-chain acylated derivatives of lysine or arginine). It may also be a dipeptide (e.g. Nxcex1-acylated derivatives of dipeptides comprising any combination of lysine, arginine or histidine and a neutral or acidic amino acid) or a tripeptide (e.g. an Nxcex1-acylated derivative of a tripeptide comprising any combination of a neutral amino acid and two charged amino acids). The polar head group may also be selected from the group of betaines, i.e. amphoteric compounds where the basic group is quarternary ammonium, sulfonium or phosphonium and the acidic group is carboxylate, carboxyalkyl, sulfonate or propanesulfonate. Finally, the detergent may be selected from, the group of imidazoline derivatives. It is preferred, however, that the detergent is not dodecyl phosphocholine.
An example of a suitable composition according to the invention is one comprising about 0.5-2.5 mg of peptide per ml, e.g. about 1 mg of peptide per ml, and about 1-3 mM, e.g. about 2 mM of the detergent, e.g. lauroyl or myristoyl lysophosphatidylcholine.
The stable aqueous, injectable solutions of glucagon and GLP-1 compounds according to the invention may be prepared by bringing together the peptide, water and a stabilizing and solubilizing amount of detergent. Typically, the solutions will contain other excipients to adjust ionic strength and provide buffering capacity and antibacterial action as needed. The final peptide concentration will be at least about 0.1 mg/ml, typically about 0.2-5 mg/ml, e.g. about 0.5-3 mg/ml, and the detergent is typically employed in an amount corresponding to at least about 0.3 mole of detergent per mole of peptide, more typically at least about 0.5 mole detergent/mole of peptide and up to about 40 moles detergent/mole of peptide, typically up to about 30 moles detergent/mole peptide, e.g. about 1-20 moles detergent/mole peptide, such as about 1-10 moles detergent/mole peptide. For a given peptide and detergent and a given concentration of peptide, a person skilled in the art will readily be able to determine a suitable detergent concentration that results in the desired stabilization. lsotonic ionic strength may be provided by conventional pharmaceutically acceptable agents such as NaCl, glycerol or mannitol. pH is buffered in the desired range between about 4 and about 8, typically by using acetate, citrate or phosphate buffers at 1-10 mM concentration as is well-known in the art. Finally, when a preservative is needed, appropriate antibacterial action is secured by the addition of, typically, phenol, m-cresol or benzyl alcohol or mixtures thereof.
The compositions of the invention can be used in the treatment of various diseases that can be treated by administering glucagon, GLP-1, or analogues or derivatives thereof. The particular peptide to be used and the optimal dose level for any patient will depend on the disease to be treated and on a variety of factors, including the efficacy of the specific peptide employed, the age, body weight, physical activity, and diet of the patient, on a possible combination with other drugs, and on the severity of the case. A typical dose of GLP-1 for regulation of the blood sugar level may e.g. be about 0.5-1 mg, for example once a day. A typical dose for glucagon may be approximately 1 mg, e.g. for gastro-intestinal imaging. It is recommended that the dosage of the active compound in question be determined for each individual patient in each case by those skilled in the art.